- HOW TO CREATE A TABLE AND SET SCALE IN ORACLE APEX SQL GENERATOR
- HOW TO CREATE A TABLE AND SET SCALE IN ORACLE APEX SQL CODE
HOW TO CREATE A TABLE AND SET SCALE IN ORACLE APEX SQL CODE
The code executes slightly BEFORE the row data is inserted. The trigger fires once FOR EACH ROW that is inserted. The application code that does the insert does not need to bother with the name of the sequence. Values ('Bruce', 'Wayne', trunc(sysdate)) Insert into super_emp (first_name, last_name, hire_date) Values (null, 'Tony', 'Stark', trunc(sysdate)) Then insert into the table using either a NULL value or without the ID column. It creates a trigger very similar to the one above (I removed a select from dual in favour of a direct assignment). The table context menu (rightclick) has an entry to create a PK trigger based with a sequence. The Oracle SQL Developer has a very nice wizard that helps to quickly create such a trigger. The NEXTVAL pseudocolumn was used directly in the values section of the insert statement.Ĭreate a table trigger that fires during insert (pre 12c solution) Values (emp_seq.nextval, 'Clark', 'Kent', trunc(sysdate)) Values (emp_seq.nextval, 'Peter', 'Parker', trunc(sysdate)) Insert into super_emp (id, first_name, last_name, hire_date) Then call nextval directly in an insert statement We then use this sequence to provide ID values for our super-employees. Experienced developers might want to skip those basic examples.įirst create a sequence using all default settings. If you are new to the concept of Oracle sequences, then I suggest to go to and try out the next few examples there by yourselfs. The standard usage of a sequence simply is to provide values for an ID column in the most performant way. We can do that with a database trigger, as an identity column or directly in an insert statement. One of the best ways to supply values for such a surrogate key column ( ID) is to use a sequence object and call the NEXTVAL function (pseudocolumn) on it. Using a surrogate key it is possible to change this invoice number without having to change all dependent records (like invoice positions) as well. In general this number is immutable, however it could be that there was some typo or scanner fault while the invoice was registered into the system. The business key might be the invoice number. For example we might have an INVOICE table. But if it happens, then the relationship is ensured by the foreign key still pointing to the surrogate key. And this integrity rule is ensured even if something changes with regards to the business key. The main advantage of a surrogate (meaningless technical) key is that the database can use it to ensure referential integrity. Then we can use it to deduct when an employee was hired and what the order among different employees is. If we want to make qualified statements, then we must add the needed information to the data. “Employee ID=17 was hired before Employee ID=26 because he/she has a lower ID”. No intrinsic meaning also implies that we can not use this ID value to make business decisions dependend on it.įor example the following sentence should be considered a wrong deduction. It’s only use is to identify (= ID) a database record in a table. Opposed to a natural key, a surrogate key has no intrinsic meaning. The most common sequence usage is as technical values for ID columns. In cases where I say “sequence” without additional specification details, I will mean the sequence object. The relevant words will be written in italics to hint about the specific interpretation in that sentence.
![how to create a table and set scale in oracle apex sql how to create a table and set scale in oracle apex sql](https://s1.o7planning.com/en/10443/images/1351946.png)
![how to create a table and set scale in oracle apex sql how to create a table and set scale in oracle apex sql](https://orclqa.com/wp-content/uploads/2020/07/create-table-apex-1024x921.png)
“This list is in sequence” often means that we have an ordered list of numbers without gaps (math: monoton increasing integer values).įor the remainder of the document I will try to make always clear which meaning I am referring to. Meaning c) an attribute for a list of numbers, stored typically in an IDcolumn
![how to create a table and set scale in oracle apex sql how to create a table and set scale in oracle apex sql](https://docs.oracle.com/cd/E59726_01/doc.50/e39150/img/sql_c.png)
Meaning b) the number valuethat is retrieved via mySeq.nextval
HOW TO CREATE A TABLE AND SET SCALE IN ORACLE APEX SQL GENERATOR
Meaning a) The sequence objectin the database aka the number generator It can mean several slightly different things. Many of the misunderstandings come from how we use the word “sequence”. I will cover the most common things here. There are also a lot of parameters that the sequence object has and that you can use to tweak the behaviour. The following post wants to give a detailed overview about what are sequences, why they work as they do, and how we should use them. Sometimes even experts tell you things about sequences that are easy to misunderstand, especially if we look into the details. There are still a lot of misunderstandings about Oracle sequences.